Erythema and tanning as human body reactions to ultraviolet radiation tend to be considered as phenomena caused by exposure to ultraviolet radiation only. However, it is considered that more complicated immune phenomena are actually caused by simultaneous exposure to visible radiation and infrared radiation as well as ultraviolet radiation. In this sense, an apparatus is necessary that can detect only ultraviolet radiation with high sensitivity under exposure to light including visible radiation and infrared radiation as well as ultraviolet radiation in developing sun protection products for protecting human bodies from ultraviolet radiation.
Conventionally, however, no ultraviolet radiation detector has been available as a product that separates and evaluates only the effect of ultraviolet radiation under exposure to visible radiation and infrared radiation as well. Therefore, conventional ultraviolet radiation detectors adopt the method of eliminating the effect of visible radiation in detection by attenuating visible radiation by subjecting a light beam emitted from a white light such as a xenon lamp to an ultraviolet radiation transmission filter, exposing a measurement sample to the light beam with the attenuated visible radiation, and spectrally splitting the light beam reflected from or passing through the measurement sample using a spectrometer.
For example, there is an apparatus that calculates the in vitro predicted SPF, frequently used as an index of the ultraviolet radiation protection effect, by measuring the intensity of ultraviolet radiation that has passed through a sun protection product. (See, for example, Patent Document 1). However, the conventional apparatus fails to detect faint ultraviolet radiation with good sensitivity because of its low ultraviolet radiation detectivity due to poor wavelength resolution or low detectivity resulting from a low signal amplification factor.
Further, such ultraviolet radiation detectors as described above employ photodetectors also sensitive to light beams other than ultraviolet radiation, such as silicon photodiode detectors, photomultipliers, and CCD cameras. Therefore, attempts have been made to extract only ultraviolet radiation using various combinations of ultraviolet radiation transmission filters in order to evaluate only the effect of ultraviolet radiation.    [Patent Document 1] U.S. Pat. No. 3,337,832